Updated script src for example

[Terrib1e]

Not a super important update, but I updated script src for Cell JS example. The download file for 'Download and Try it!" (cell_sync.html) also needs to have its src updated.

[coveralls]

Coverage remained the same at 82.979% when pulling af943b5 on Terrib1e:patch-2 into 01ab402 on intercellular:develop.

[gliechtenstein]

Thanks for the PR! I think this needs explanation.

I decided to keep the https://www.celljs.org/cell.js around in the documentation because these shouldn't depend on certain snapshot of a version. Otherwise we would have to update these examples whenever we make a new release. Right now the latest version is 1.1.1 but once I make another release it will be 1.1.2 or above, and I don't think we should have to go back and update this every time.

Just to clarify (I don't think I mentioned this anywhere before), the https://www.celljs.org/cell.js is always the cell.js file from the latest gh-pages branch, which means it will always be the most up to date version, so I think the examples in the README should consistently work unless we break something.

But I do appreciate the PR. I'll close this since I won't be merging it this time, but please keep it coming!